An airtightly sealing cap for sealing an electronic component storing package such as an SMD (Surface Mount Device) package (surface mount device package) employed for airtightly sealing an electronic component such as a SAW filter (surface acoustic wave filter) employed for noise reduction of a portable telephone or the like or a quartz resonator is known in general. An airtightly sealing cap including a brazing filler metal layer composed of Au and Sn is known as the airtightly sealing cap. Such an airtightly sealing cap is disclosed in each of Japanese Patent Laying-Open No. 2002-9186 and Japanese Patent Laying-Open No. 2000-68396, for example.
In relation to a brazing filler metal described in the aforementioned Japanese Patent Laying-Open No. 2002-9186, a brazing filler metal layer in which an Sn plating layer and an Au plating layer or an Au—Sn alloy plating layer are alternately stacked is so formed that the content of Au is 60 mass % to 85 mass %. This brazing filler metal described in Japanese Patent Laying-Open No. 2002-9186 conceivably has a thickness of at least 16 since an Au plating layer of 8 μm and an Sn plating layer of 8 μm are alternately stacked.
In relation to a brazing filler metal described in the aforementioned Japanese Patent Laying-Open No. 2000-68396, a brazing filler metal in which an Au layer and an Sn layer or an Sn-10% Au layer are so stacked that the content of Au is 63% to 81% in the brazing filler metal after heat treatment is disclosed.
Following miniaturization of a device (electronic component), an electronic component storing package storing the device and an airtightly sealing cap for sealing the electronic component storing package have also been miniaturized in recent years, and hence the quantity (thickness) of a brazing filler metal necessary for sufficiently bonding the electronic component storing package and the airtightly sealing cap to each other gets fewer (smaller).
In a brazing filler metal in which Au is employed similarly to the brazing filler metal described in each of the aforementioned Japanese Patent Laying-Open No. 2002-9186 and Japanese Patent Laying-Open No. 2000-68396, reduction of the usage of Au is demanded since Au is extremely high-priced.
However, the brazing filler metal described in the aforementioned Japanese Patent Laying-Open No. 2002-9186 has the thickness of at least 16 μm, and hence there is such a problem that the usage of Au increases as the brazing filler metal for sealing a miniaturized electronic component storing package.
In the aforementioned Japanese Patent Laying-Open No. 2000-68396, no specific structure such as the composition of the brazing filler metal before heat treatment (before sealing) is disclosed, and a technical idea of reducing the usage of Au in the brazing filler metal for sealing a miniaturized electronic component storing package is neither disclosed nor suggested.